Movable bed stratifier with constant pneumatic current



Aug. 20, 1957 D. WESTON ETAL I MOVABLE BED STRATIFIER WITH CONSTANT PNEUMATIC CURRENT Filed May 25, 1954 1 mm NN 3 Sheets-Sheet 1 A 7-70 ZNtfXS' 1957 D. WESTON ETAL 2,803,346

MOVABLE BED STRATIFIER WITH CONSTANT PNEUMATIC CURRENT Filed May 25, 1954 3 Sheet-Sheet 3 H7 1 72% i; i 1

65" t 52 18b L27 in I I MOVABLE BED STRATEFIER WITH CONSTANT PNEUMATIC CURRENT David Weston, Toronto, Ontario, and Arthur R. MacPhersou, Ottawa, Ontario, Canada Application May 25, 1954, Serial No. 432,199 Claims priority, application Canada April 30, 1954 4 Claims. (Cl. 209466) This invention relates to a method and apparatus for classifying dry particulate material into a fraction made up of particles having a relatively high surface-weight ratio and one where the particles have a relatively low surface-weight ratio. While the method and apparatus were particularly designed to remove opened asbestos fibre bundles from host rock and unopened fibre bundles, the invention is by no means limited to the treatment of asbestos ore.

The objects of the invention are to provide a method and apparatus for quickly and efiectively classifying dry materials into the fractions mentioned in the preceding paragraph, whereby a single machine according to the invention, or a small number of such machines, may be utilized to handle tonnages which, using prior art techniques, called for an appreciably larger number of units.

We have discovered that the desired classification can be effected very quickly in a chamber provided with an air-permeable separating deck along which a bed of the material is conveyed by the application of mechanical movement to the bottom of the bed while air under pressure is directed upwardly through the deck. The airflow and mechanical movement act in conjunction to stratify the bed of material, during its travel along the deck, into strata wherein the particles are characterized by surfaceweight ratios which decrease with proximity to the deck. Suction is applied above the deck and the upper strata, i. e. a fraction of the material made up of particles having a relatively high surface-weight ratio, is drawn 01f upwardly in an airstream, and the remaining material is discharged at the end of the deck remote from the feed end. The chamber is preferably operated at a subatmospheric pressure.

The method of our invention may be generally defined as a method of classifying dry material into a fraction made up of particles having a relatively high surfaceweight ratio and a fraction made up of particles having a relatively low surface-weight ratio, which comprises forming a relatively shallow bed of the material, continually advancing said bed by the application of mechanical movement to the bottom thereof, continuously maintaining the bed by adding new material at the upstream end thereof, continuously feeding a gaseous medium upwardly through said bed whereby to cause said bed, as it advances, to stratify under the joint influence of said mechanical movement and the upward passage of the gaseous medium through the bed, continuously applying suction to the top of the bed across the width thereof at a point adjacent the downstream end of the bed to remove upwardly and carry away by entrainment a stratified fraction of the material, said fraction being made up of particles having a relatively high surface-weight ratio, and continuously discharging the fractionof said bed remaining after the upward removal of the first fraction. Of the mechanical movements which may be applied to advance the bed we prefer to use a biased reciprocatory motion of controlled amplitude such, for

atnt

Patented Aug. 20, 1957 instance, as may be produced by an electromagnetic pulse type feeding unit. Examples of this type of unit are those manufactured by the Syntron Company of Homer City, Pennsylvania, United States of America. Other suitable motions which may be employed are shaking and vibrating such as may be produced by other types of vibratory devices, rotating cams, eccentrics and the like.

The invention includes apparatus specially adapted to carry out the process of the preceding paragraph. This apparatus comprises a rigid supporting frame, an airdistributing manifold rigidly mounted in the lower portion of said frame, said manifold having a plurality of air-delivery ports, a hood section rigidly mounted in the upper portion of said frame, a vibrating section suspended independently of said hood section and said air-distributing manifold and located between said hood section and said manifold, vibratory feeder means suspended from said frame and secured to said vibrating section for vibrating the latter, said vibrating section including an air-permeable separating deck, said air-delivery ports being arranged to feed air through said air-permeable separating deck, said vibrating section being connected with said hood section and with said manifold by means of air-tight seals, each seal including a section of resilient material disposed so as to obviate transference of the vibratory motion of the vibrating section to either said hood section or said air-distributing manifold, means for feeding air under pressure to said manifold, inlet means for feeding material to one end of said separating deck, means adjacent the other end of the deck for upwardly withdrawing a classified fraction of the material fed therealong, and means at said other end of the deck for discharging the remaining material, said means for withdrawing material upwardly comprising a suction means located at a point remote from said bed and a conduit connected to said suction means, said conduit extending through said hood section toward said separating deck and terminating at a point adjacent, but spaced from, said deck.

In drawings which illustrate a preferred embodiment of the invention:

Figure 1 is a side elevation,

Figure 2 is a central longitudinal section showing on a more generous scale the portions of the apparatus where the classification occurs,

Figure 3 is an end elevation with the vibratory feeder removed,

Figure 4 is a top plan view of the upper seal, and

Figure 5 is a top plan view of the lower seal.

Referring first to Figures 1 and 2, the main parts of the apparatus are supporting frame 10, air-distributing manifold 11, hood section 12, vibrating section 13, vibratory feeder 14, feed inlet 15 provided with airlock 16, conduit 17 for carrying off one classified fraction in an airstream, discharge port 18 for removing the remaining material, cyclonic product collector 19, suction fan 20, air-delivery blower 21, upper seal 22, and lower seal 23. The arrangement and nature of these parts will now be described in greater detail.

The supporting frame 10 is made up of a base 25; a pair of beams 26 extending transversely across said base and rigidly supporting air-distributing manifold 11; four vertical beams 27; a pair of horizontal beams 28 forming, in conjunction with transverse beams 29 and panels 29a (see Figure 3), the upper portion of the frame; and bracing members 30.

The vibrating section 13, and the vibratory feeder 14 attached thereto by the arms 31, are freely suspended from the horizontal beams 28 in the following way. L-shaped brackets 32 are mounted on the opposite sides of vibratory feeder 14. Eye-bolts 33 are mounted in brackets 32 and are provided with compression springs 34 and retaining nuts 35. A second pair of eye-bolts 36 are attached to corresponding ends of beams 28, and the vibratory feeder'14 is suspended by cables 37 passed through the eyes of the bolts 33 and 36.: At the other ends of beams 28, another pair of eye-bolts are provided. These bolts have been labelled 38, and they each anchor a cable 39 which supports'the end of the vibrating section 13 opposite the vibratory feeder 14, by virtue of rectangular box-like base 42 having a plurality of similar rectangular openings in its top wall. Mounted in each of :these rectangular openings'is a rectangular conduit 43. Each conduit43 is provided with a damper 44, and the dampers are mounted on shafts 45 which extend transversely across the box-like base 42. Shafts 45 are rotatably mounted in bearing pads 46 secured to the side walls of box 42, and each shaft 45 has secured to it an adjusting arm 47, whereby the shafts. may be turned to vary the settings of the dampers 44 in the conduits 43.

Manifold 11 includes, above box-like base 42, a rectangular seating 48 for lower seal 23. A conduit 21a leads from blower 21 into base 42 of manifold 11.

Seal 23 is a thick rectangular section of soft resilient material such as foam rubber, and is provided near its upper surface with a metallic reinforcing layer 49, sheet aluminum being preferred. The seal must of course be formed to permit passage of air upwardly from the manifold 11 to the vibrating section, and it is therefor provided with a number of rectangular passageways 43a located to match the positioning of the rectangular conduits 43.

The vibrating section 13 has side walls 50, to which the feeder arms 31 are rigidly secured, and opposite end walls 51 and 52. 'Discharge port 18 is located in the lower portion of end wall 52. The upper edges of side walls 50 and end walls 51 and 52 are each provided with an outwardly extending lip or flange 53, provided to supportthe lower surface of upper seal 22. Upper seal 22 is, like lower seal 23, a thick rectangular section of resilient material such as foam rubber, and is also provided, near the surface thereof which faces vibrating section 13, with a metallic reinforcing layer, as best seen at 54 in Figures 2 and 4.

Side walls. 50, and end walls 51 and 52, of vibrating section 13, are connected along their lower edges to a rectangular, generally horizontally disposed, separating deck indicated by reference numeral 55. Deck 55 is made up of a large number of narrow bars 56, set upon their edges and running longitudinally of the bed, and a number of bars 57 extending transversely across the deck beneath the bars 56. The bars 56 run parallel to one another and are spaced closely adjacent one another to permit passage of air therebetween without allowing material being classified to escape downwardly between the bars. When vibratory feeder 14 is actuated the whole of vibrating section 13, i. e. side walls 50, end walls 51 and 52, and the deck 55 made up of bars 56 and 57, is vibrated.

We do not propose to provide any detailed description of the vibratory feeder 14 since such feeders are known per se and any vibratory feeder may be employed which is capable of directionally vibrating the vibrating section 13, i. e. imparting biased reciprocation to the section so that material fed to one end of the deck is caused to travel towards the other end thereof.

The discharge port 18 leads, via a flexible conduit 18a, to a discharge chute 18b rigidly mounted between two of the vertical posts 27 of frame 10. The end of chute 18b is substantially sealed against the admissionof air, by the provision of a flexible rectangular skirt 180 formed of rubber or comparable material and secured, along its upper edge only, to the chute 18b. With this arrangement, whenever an appreciable weight of material builds up in the chute behind the skirt the materials weight will force the skirt open and permit the material to escape, and, once the material has escaped, the skirt will reassume its vertical sealing position until forced to reopen by the weight of a new batch of material. According to an alternative arrangement the skirt may be set to permit continuous discharge of the material, or a rotary air-lock may be employed.

.The hood section 12 is rigidly mounted in the upper portion of frame 10, directly above vibrating section 13. The hood 12 is generally rectangular and is made up of side walls 60, and end walls 61 and 62. The hood is provided around its base with a rectangular seating 63 for upper seal 22. Hood section 12 includes a hopper portion 64 provided with the feed inlet 15 and an inspection door 65;

and the hood includes a roof portion 66 which extends between hopper portion 64 and conduit 17 and slopes downwardly towards the lower end of the conduit. A wall 67 extends vertically upward from each longitudinal edge of roof portion'66; and each wall 67 is provided with two series of vertically aligned holes 68 and 69, whereby the vertical disposition of roof 66 may be adjusted by passing bolts 70 through side walls 60 of hood section 12 and a selected hole in each series 68 and 69 in each wall 67.

A wall 68a extends vertically upwardly from the lower edge of roof 66, and the conduit 17 is mounted between this wall 68a and the end wall 61 of the hood section. The height of the lower end of conduit 17 above the separating deck 55 is adjustable due to the provision of three bolts 71 rigidly secured to conduit 17, and three vertical slots 73 in end wall 61. During vertical adjustment of the conduit the bolts 71 ride in the slots, and, when the desired position has been reached, nuts 74 carried by the bolts 71 are tightened to clamp the conduit in position. Conduit 17 is provided, silghtly above the level of the hood section 12, with a pair of oppositely disposed inspection ports 75. 7

Having described the structural nature of the preferred embodiment of the invention shown in the drawings, we

The blower 21 and suction fan 20 are turned on and their speeds and intake openings adjusted, along with the settings of dampers 44, to provide a sub-atmospheric pressure within the apparatus, and to provide for removal of air' via conduit 17 at .a rate suflicient for entrainment of all separated asbestos fibre at the'contemplated rate of feed. The air from blower 21 travels along conduit 21a and enters box 42, whence it is fed upwardly through conduits 43 and passageways 43a and passes between bars 56 of separating deck 55.

The vibratory feeder 14 is energized and the mixture to be separated is then fed, via air-lock 16, inlet opening 15, and hopper portion 64, onto the end of the vibrating separating deck 55 adjacent end wall 51. A relatively shallow bed of the mixture forms on deck 55 and advances toward the opposite end of the deck under the influence of the directional vibratory motion being imparted to the vibrating section. As the mixture travels along the bed it is not only affected by the vibration but also. affected by the classifying effect of the air from manifold 11 sweepingupwardly through the bed. Under the joint rock and unopened fibre bundles leads to very clear Stratification into the layers described.

As the bed passes beneath conduit 17, the upper layer of opened fibre is drawn upwardly by suction and entrained in the stream of air being drawn through the conduit by the fan 20. As this airstream passes through cyclone 19 the fibre carried in the stream is collected in known manner, as the cyclones apex discharge.

After the withdrawal of the opened fibre layer the remaining portion of the bed is gravity discharged through port 18, conduit 18a, and discharge chute 1%.

While the case of asbestos has been particularly mentioned in this specification, the method and apparatus of the invention may be used in the treatment of other ores or materials, since all that is required for stratification in the bed is that the particles which are to be separated have fairly pronounced differences either in specific gravity or in surface area. The combined airflow and vibration employed effects stratification in accordance with the tendency of particles which are specifically light, or

of relatively large surface area, to rise to the top of the bed, and the tendency of particles which are specifically heavy or of comparatively small surface area, to work their way to the lower levels of the bed.

What we claim as our invention is:

l. A dry material classifying apparatus comprising; a rigid supporting frame; an air-distributing manifold rigidly mounted in the lower portion of said frame, said manifold having a plurality of air-delivery ports; a hood section rigidly mounted in the upper portion of said frame; a vibrating section suspended independently of said hood section and said air-distributing manifold and located between said hood section and said manifold; vibratory feeder means suspended independently of said hood section and said air-distributing manifold and secured to said vibrating section for vibrating the latter; said vibrating section including an air-permeable separating deck, said air-delivery ports being arranged to feed air through said air-permeable separating deck; air-tight seals connecting said vibrating section with said hood section and with said manifold, each said seal including a thick section of soft resilient material disposed so as to obviate transference of the vibratory motion of the vibrating section to either said hood section or said air-distributing manifold; means for feeding air under pressure to said manifold; inlet means for feeding material to one end of said separating deck; means adjacent the other end of the deck for upwardly withdrawing a classified fraction of the material fed therealong; and means at said other end of the deck for discharging the remaining material; said means for withdrawing material upwardly comprising a suction means located at a point remote from said bed and a conduit connected to said suction means, said conduit extending through said hood section toward said separating deck and terminating at a point adjacent, but spaced a predeterminable distance from, said deck.

2. An apparatus as defined in claim 1, in which said hood section includes a roof portion which extends between said inlet means and said conduit and slopes downwardly towards said conduit, and means for adjusting the vertical disposition of said roof portion.

3. A dry material classifying apparatus comprising; a rigid supporting frame; an air-distributing manifold rigidly mounted in the lower portion of said frame, said manifold having a plurality of air-delivery ports; a hood section rigidly mounted in the upper portion of said frame; a vibrating section suspended independently of said hood section and said air-distributing manifold and located between said hood section and said manifold; vibratory feeder means suspended independently of said hood section and said air-distributing manifold and secured to said vibrating section for vibrating the latter; said vibrating section including an air-permeable separating deck comprising a plurality of closely spaced narrow bars running parallel to one another and arranged longitudinally of the bed, said air-delivery ports being arranged to feed air through said air-permeable separating deck; air-tight seals connecting said vibrating section with said hood section and with said manifold, each said seal including a thick section of soft resilient material disposed so as to obviate transference of the vibratory motion of the vibrating section to either said hood section or said airdistributing manifold; means for feeding air under pressure to said manifold; inlet means for feeding material to one end of said separating deck; means adjacent the other end of the deck for upwardly withdrawing a classified fraction of the material fed therealong; and means at said other end of the deck for discharging the remaining material; said means for withdrawing material upwardly comprising a suction means located at a point remote from said bed and a conduit connected to said suction means, said conduit extending through said hood section toward said separating deck and terminating at a point adjacent, but spaced a predeterminable distance from, said deck.

4. A dry material classifying apparatus comprising; a rigid supporting frame; an air-distributing manifold rigidly mounted in the lower portion of said frame, said manifold having a plurality of air-delivery ports; a hood section rigidly mounted in the upper portion of said frame; a vibrating section suspended independently of said hood section and said air-distributing manifold and located between said hood section and said manifold; vibratory feeder means suspended independently of said hood section and said air-distributing manifold and secured to said vibrating section for vibrating the latter; said vibrating section including an air-permeable separating deck, said air-delivery ports being arranged to feed air through said air-permeable separating deck; air-tight seals connecting said vibrating section with said hood section and with said manifold, each said seal comprising a thick layer of foam rubber provided with a reinforcement adjacent the surface of the seal which faces the vibrating section, said section of resilient material being disposed so as to obviate transference of the vibratory motion of the vibrating section to either said hood section or said airdistributing manifold; means for feeding air under pressure to said manifold; inlet means for feeding material to one end of said separating deck; means adjacent the other end of the deck for upwardly withdrawing a classified fraction of the material fed therealong; and means at said other end of the deck for discharging the remaining material; said means for withdrawing material upwardly comprising a suction means located at a point remote from said bed and a conduit connected to said suction means, said conduit extending through said hood section toward said separating deck and terminating at a point adjacent, but spaced a predeterminable distance from, said deck.

References Cited in the file of this patent UNITED STATES PATENTS 2,345,866 Brentz Apr. 4, 1944 2,512,422 Fletcher June 20, 1950 FOREIGN PATENTS 455,219 Great Britain Oct. 12, 1936 1,038,080 France May 6, 1953 

